The Nile River Basin from SRTM data

Someone asked the other day whether the cross-platform, free and open-source GIS Whitebox GAT can handle watershed delineation from massive, regional-scale DEMs. They had a particular interest in the Nile River basin. Heck, if you’re going to go big, why not go huge, right? So I decided to give it a go. First off, I used the Retrieve SRTM Data tool to download the approximately 800 SRTM 3-arcsecond (approximately 90 m) tiles that make up the Nile River basin. This required a bit of experimentation because my first attempt at doing so hit the boundary of the basin and I had to give it a second try. The tool downloaded each of the tiles and mosaicked them into a single large DEM. The final DEM was 45,601 rows by 25,201 columns (a little over 1.1 billion grid cells) and was 4.28 GB in size. I then used the new Breach…